As spring arrives each year, it is important to pay attention to your alfalfa fields as they begin to green up and grow. It is time to look for signs of “winterkill.” Winterkill is the generic term used to describe death of an alfalfa stand from fall through spring. However, the name is misleading because most stand death happens during the spring. There are many reasons why alfalfa dies out over the winter and in the early spring. Each of our agronomists sounded the same message around the importance of checking stands for winterkill each spring.

Nebraska Update from Dave Olson, Sales Agronomist: Last summer’s extended period of dry weather left many alfalfa stands stressed and mildly nutrient deficient. When the rain did come, it persisted until the soil profile was nearly saturated. Then what happened? Well, Scott Frost was great news for the Cornhusker’s football team, but “Jack Frost” started a long cycle of freezing and thawing that certainly was not what the already stressed stands needed. Most of southern Nebraska areas entered the fall without the abundant moisture that northern Nebraska had. Plus, the southern half of the state had far less snow cover to protect from the extreme cold of winter. Each region of the state has different reasons to raise concerns about winter survival; however, it’s going to be important for everyone to assess each field by digging roots and making careful observations throughout the entire field.

Rotate or Leave it?

The decision to rotate a field can be hard to make with the irregular patterns of dead areas.The rule of thumb is rotate if the field falls below the average of 40 stems/square foot. We recommend using a larger size hoop than the simple 1-foot squares that are often available and used. A larger circle will give you a better representation. Be sure to sample several areas of the field until you feel comfortable with the numbers you are collecting.

Be sure to keep an eye on the stand quality throughout the summer as well. Additional mechanical damage from haying equipment to damaged crowns and taproots can cause additional loss throughout the summer, so keep that in mind.

If you have questions or would like help in this decision-making process, please contact your local Legend Seeds representative for guidance.

Examples of Winterkill Situations

Example of winterkill with crowns & taproot
Concerns: A few of the agronomists mentioned the crowns heaving or pushing out of the ground. See an example of this condition at right. When there is more than a half-inch of exposed root below the crown, then there is a very high probability that the taproot has been severed and the alfalfa plant will die shortly after greening up in the spring. Sometimes, the taproot gets severed deep enough that the plants will yield close to normal initially, but when cut for the first time the stand will never green up again.

Examples of winterkill from ponded water:

Example of winterkill from cold soil temperatures: